The present invention relates to water level control systems for controlling the level of water in a container to which water is added continuously or periodically. The invention relates more particularly to water level control systems intended for maintaining a desired water level in an aquarium. A water level control system according to the invention is primarily intended for use in an aquarium skimmer box assembly.
A skimmer box assembly is a device used by aquarists for, as the name indicates, skimming water from the surface of the body of water in an aquarium without the need for drilling holes in the walls or bottom of the aquarium. The basic structure of a skimmer box assembly includes an inlet tank, a siphon tube and an outlet tank, normally with the inlet tank attached to the outlet tank with some means. The skimmer box assembly is mounted on the frame of the aquarium with the inlet tank partly immersed in the aquarium water.
The inlet and outlet tanks are filled with water and the siphon tube is "started" by evacuating air from the siphon tube so that it fills with water. One simple starting technique is to insert one end of a small tube into the outlet end of the siphon to a point near the highest point of the siphon and to then apply suction to the other end of the tube until the air has been evacuated. After the siphon has been started, water will flow through the siphon tube as long as the water level in the inlet tank is higher than the water level in the outlet tank. As long as the siphon tube remains filled with water, the siphon tube provides the fluid connection between the aquarium and the outlet tank.
In operation, water is pumped into the aquarium from a filtration system located below or behind the aquarium. The water level in the aquarium rises and water from the aquarium flows into the inlet tank. The water level in the inlet tank rises, creating a differential pressure between the inlet tank and outlet tank and forcing water through the siphon tube into the outlet tank on the outside of the aquarium. The outlet tank typically has some means of maintaining a selected water level combined with a means for draining water out of the outlet tank into the filtration system.
A conventional skimmer box assembly is illustrated in FIGS. 1 and 2. This assembly includes an inlet tank 2 attached to an outlet tank 4 by conventional attachment means 6 which in the illustrated assembly are composed of horizontally extending screws secured to outlet tank 4 and wing nuts which clamp inlet tank 2 to outlet tank 4. The assembly is placed on a frame 8 at the upper edge of an aquarium tank 10 with inlet tank 2 inside tank 10 and partly immersed in the aquarium water (not shown) and outlet tank outside tank 10. The upper edge of inlet tank 2 has an array of slots to allow aquarium water to flow into tank 2. A siphon tube 12 extends between tanks 2 and 4 and passes over frame 8.
As shown in FIG. 2, outlet tank 4 has a weir 20 which extends across the entire width of tank 4, perpendicular to the aquarium tank wall which separates tank 2 from tank 4. Weir 20 has an upper edge 22 located below the top of tank 4 and generally in a region midway between the top and bottom of tank 4. Weir 20 divides the lower portion of tank 4 into a siphon chamber and an outlet chamber. The siphon chamber receives the outlet end of siphon tube 12.
The outlet chamber contains a filter pad 26, a flow tube 28 and a flow tube fitting 30 in which flow tube 28 is retained. Typically, filter pad 26, located on top of flow tube 28, is made of a reticulated polyester foam. Fitting 30 extends through an opening in the bottom of tank 4 and is attached, beneath tank 4, to a further fitting 32 which is provided for connection of a hose or tube that will extend, in a known manner, to an aquarium water sump. An O-ring 34 may be provided between fitting 30 and the bottom of tank 4 to seal the opening in the bottom of tank 4.
The skimmer box assembly is installed by placing tank 4 on frame 8 and placing tank 2 in the aquarium and attaching it to tank 4 by attachment means 6. The aquarium is filled to a level above the bottom of the slots on inlet tank 2, so that tank 2 becomes filled with water. The user fills outlet tank 4 with water to the level of top 22 of weir 20. Then, siphon tube 12 is placed between the inlet tank and the siphon chamber of outlet tank 4 and the air in siphon tube 12 is evacuated, in the manner described earlier herein, filling siphon tube 12 with water. This removal of air starts siphon tube 12, initiating a flow of water through tube 12. If water is not being pumped into aquarium tank 10, water will flow into inlet tank 2 until the water level in aquarium tank 10 descends to the level of the bottoms of the slots in inlet tank 2. Flow through tube 12 will continue until the same water level is established in inlet tank 2 and outlet tank 4, which level corresponds to the level of top 22 of weir 20, with the excess water flowing over top 22, into the outlet chamber and then out of tank 4 via tube 28. Water exiting tank 4 will normally flow to a filtration system located below the aquarium (not shown).
When the pump in the filtration system is started, water flows into aquarium tank 10, causing the water level in tank 10 to rise. Water flows into inlet tank 2, raising the water level therein and causing water to flow through siphon tube 12 and into outlet tank 4. The water level in the siphon tube compartment of the outlet tank rises, overflowing top 22 of weir 20. Water passes through filter pad 26, raising the water level in the outlet chamber. When the water level in the outlet chamber rises above the top of flow tube 28, water drains out of outlet tank 4, through fittings 30 and 32 and a hose connected to fitting 32, to the filtration system located below the aquarium.
Filter pad 26 filters debris as well as partially muffling the noise from the water and air mixture exiting outlet tank 4. The noise occurs when a vortex (whirlpool) in the water above flow tube 28 comes into communication with air in tube 28, thus allowing audible noise to "escape" from tube 28. Typically, for a flow tube with a one inch inside diameter, continuous noise begins to occur at flows above, for example, 300 gallons per hour. This noise can be very loud and is quite distracting if the aquarium is located in a quiet room.